Treo: Textual Syntax for Reo Connectors

Reo is an interaction-centric model of concurrency for compositional specification of communication and coordination protocols. Formal verification tools exist to ensure correctness and compliance of protocols specified in Reo, which can readily be (re)used in different applications, or composed into more complex protocols. Recent benchmarks show that compiling such high-level Reo specifications produces executable code that can compete with or even beat the performance of hand-crafted programs written in languages such as C or Java using conventional concurrency constructs. The original declarative graphical syntax of Reo does not support intuitive constructs for parameter passing, iteration, recursion, or conditional specification. This shortcoming hinders Reo's uptake in large-scale practical applications. Although a number of Reo-inspired syntax alternatives have appeared in the past, none of them follows the primary design principles of Reo: a) declarative specification; b) all channel types and their sorts are user-defined; and c) channels compose via shared nodes. In this paper, we offer a textual syntax for Reo that respects these principles and supports flexible parameter passing, iteration, recursion, and conditional specification. In on-going work, we use this textual syntax to compile Reo into target languages such as Java, Promela, and Maude.Comment: In Proceedings MeTRiD 2018, arXiv:1806.0933

Relating BIP and Reo

Coordination languages simplify design and development of concurrent systems. Particularly, exogenous coordination languages, like BIP and Reo, enable system designers to express the interactions among components in a system explicitly. In this paper we establish a formal relation between BI(P) (i.e., BIP without the priority layer) and Reo, by defining transformations between their semantic models. We show that these transformations preserve all properties expressible in a common semantics. This formal relation comprises the basis for a solid comparison and consolidation of the fundamental coordination concepts behind these two languages. Moreover, this basis offers translations that enable users of either language to benefit from the toolchains of the other.Comment: In Proceedings ICE 2015, arXiv:1508.0459

Exposing latent mutual exclusion by work automata

A concurrent application consists of a set of concurrently executing interacting processes. Although earlier we proposed work automata to specify both computation and interaction of such a set of executing processes, a detailed formal semantics for them was left implicit. In this paper, we provide a formal semantics for work automata, based on which we introduce equivalences such as weak simulation and weak language inclusion. Subsequently, we define operations on work automata that simplify them while preserving these equivalences. Where applicable, these operations simplify a work automaton by merging its different states into a state with a ‘more inclusive’ state-invariant. The resulting state-invariant defines a region in a multidimensional real vector space that potentially contains holes, which in turn expose mutual exclusion among processes. Such exposed dependencies provide additional insight in the behavior of an application, which can enhance scheduling. Our operations, therefore, potentially expose implicit dependencies among processes that otherwise may not be evident to exploit

Protocol scheduling

Interactions amongst different processes in concurrent software are governed by a protocol. The blocking I/O operations involved in a protocol may temporarily suspend the execution of some processes in an application. Scheduling consists of the allocation of available processors to the appropriate non-suspended processes in an application, such that some specified criteria (e.g., shortest execution time or highest throughput) are met. We use a generic, game-theoretic scheduling framework to find optimal non-preemptive schedules for an application. We then show how such schedules themselves can be encoded as protocols, which in our framework, can be composed with the original application protocol. The resulting composed protocol restricts the number of ready processes to the number of available processors, which enables standard preemptive schedulers of modern operating-systems to closely approximate the behavior and the performance of the optimal non-preemptive scheduler of the application. We evaluate our work by comparing the throughput of two versions of a cyclo-static dataflow network: one version with the usual protocol, and the other version with a restricted protocol

Scheduling games for concurrent systems

A scheduler is an algorithm that assigns at any time a set of processes to a set of processors. Processes usually interact with each other, which introduces dependencies amongst them. Typically, such dependencies induce extra delays that the scheduler needs to avoid. Specific types of applications, like streaming applications, synthesize a scheduler from a formal model that is aware of these interactions. However, such interaction-specific information is not available for general types of applications. In this paper, we propose an interaction aware scheduling framework for generic concurrent applications. We formalize the amount of work performed by an application as constraints. We use these constraints to generate a graph, and view scheduler synthesis as solving a game on this graph that is played between the scheduler and the application. We illustrate that our framework is expressive enough to subsume an established scheduling framework for streaming programs

Combine and conquer: Relating BIP and Reo

Coordination languages simplify design and development of concurrent systems. Particularly, exogenous coordination languages, like BIP and Reo, enable system designers to express the interactions among components in a system explicitly. A formal relation between exogenous coordination languages comprises the basis for a solid comparison and consolidation of their fundamental concepts. In this paper we establish a formal relation between BI(P) (i.e., BIP without the priority layer) and Reo, by defining transformations between their semantic models. We show that these transformations preserve all properties expressible in a common semantics. We use these transformations to define data-sensitive BIP architectures and their composition

Soft constraint automata with memory

We revise soft constraint automata, wherein transitions are weighted and each action has an associated preference value. We first relax the underlying algebraic structure to allow bipolar preferences. We then equip automata with memory locations, that is, with an internal state to remember and update information from transition to transition. We furthermore revise automata operators, such as composition and hiding, providing examples on how such memory locations interact with preferences. We finally apply our framework to encode context-sensitive behaviour

Soft constraint automata with memory

In this paper, we revise the notion of Soft Constraint Automata, where automata transitions are weighted and consequently each action is associated with a preference value. We first relax the underlying algebraic str

Relating BIP and Reo

Coordination languages simplify design and development of concurrent systems. Particularly, exogenous coordination languages, like BIP and Reo, enable system designers to express the interactions among components in a system explicitly. In this paper we establish a formal relation between BI(P) (i.e., BIP without the priority layer) and Reo, by defining transformations between their semantic models. We show that these transformations preserve all properties expressible in a common semantics. This formal relation comprises the basis for a solid comparison and consolidation of the fundamental coordination concepts behind these two languages. Moreover, this basis offers translations that enable users of either language to benefit from the toolchains of the other